However, this only affects Kate; not KWrite, Kile, KDevelop or any other application using Kate Part. If you want to disable the markers for KWrite, Kile or KDevelop, use kwriterc, kilerc or kdeveloprc instead of katerc.

In KDE >= 4.9, there is a graphical option in the editor configuration dialog in “Appearance > Borders > [x] Show line modification markers”.